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Until recently, those who desired the fastest Mac that money could buy simply sought out the one with the highest megahertz rating. But with the release of the 733MHz and dual-processor 533MHz Power Mac G4 models, speed-hungry consumers must delve a little deeper. Although the G4/733 boasts the higher megahertz rating, the dual-processor G4/533 significantly outperformed Apple's top-of-the-line Power Mac in several of our tests. And if you plan on upgrading to OS X, the dual-processor Mac is an even better choice.

It's What's Inside That Counts

Except for the type and quantity of processors, the $2,499 dual-processor 533MHz Power Mac is configured exactly like the single-processor 533MHz G4 model: with 128MB of SDRAM, a 40GB Ultra ATA hard drive, a 1MB L2 cache, a 133MHz system bus, three RAM slots, a 4x AGP slot, four 64-bit PCI slots, an internal 8x4x32x CD-RW drive, a 32MB Nvidia GeForce2 MX graphics card, gigabit Ethernet, and a 56K internal modem. Both G4s lack an audio-input port and require 133MHz RAM, so your old RAM won't work in these systems.

The $3,499 733MHz Power Mac, by contrast, carries a single G4 processor with twice the SDRAM (256MB); half again the storage (a 60GB Ultra ATA drive); a 256K L2
and
a 1MB L3 cache; a SuperDrive, which reads and writes both CDs and DVDs (at 8x4x24x, with a 2x DVD-R write speed); and a copy of iDVD, for burning DVDs. (For $500 less, Apple will substitute a CD-RW drive for the SuperDrive; we tested the SuperDrive model.)

What a Difference a Chip Makes

When multiprocessor (MP) support returned to the Mac last year, many people wondered if two slower processors working in tandem were really faster than a single processor with a higher megahertz rating. Our tests show that they can be, when running applications optimized for multiple processors.

For example, in our Adobe Photoshop tests, MP-aware operations such as Gaussian Blur and Unsharp Mask were swifter on the dual-processor 533MHz model than on the 733MHz Mac by a second or two. And in our Cinema 4D XL rendering test, the dual-processor Mac outpaced the 733MHz Mac by more than 35 percent. In situations where MP optimization doesn't matter -- such as our Speedmark, Photoshop RGB to CMYK, and SoundJam tests -- the 733MHz Mac pulled ahead of the multiprocessor machine. That faster processor didn't help much in Quake III, however, adding less than 5 percent to the overall frame rate.

Although these results may seem disheartening given the SuperDrive-bearing 733MHz Power Mac's $1,000 premium, there's a strong likelihood that these scores will change as new versions of certain applications and of Mac OS are released. That's because the 733MHz Power Mac has a more recent iteration of the PowerPC G4 processor (the 7450) than the single- and dual-processor 533MHz Macs, which have the older 7410 processor. Among other differences, the 7450 chip carries an L3 cache. But it's new enough that software developers have yet to take advantage of the chip's capabilities. Once applications and Mac OS are optimized for the 7450 chip, performance should improve.

A Super Drive

Although performance is important to every Mac user, the speed of the 733MHz Power Mac may be a secondary consideration for those interested in creating DVDs to play back on home DVD players. At present, only the $3,499 Power Mac configuration includes a SuperDrive, the CD and DVD player and recorder that makes this possible.

Our experience with the SuperDrive and the accompanying iDVD was mostly positive. Although iDVD locked up during one project, in a subsequent attempt we created a DVD full of QuickTime movies in a matter of minutes. (Burning the DVD took about three times longer than the DVD's playing time.)

iDVD is easy to use, and the bundled themes let you create attractive DVDs with intuitive interfaces. While we're thrilled with this ability, iDVD has its limitations. For example, you can place only six elements on a screen, although nesting folders may help compensate. And each DVD holds only an hour of video.

Less impressive than the SuperDrive's DVD-writing capabilities is its speed. The drive is a sluggish reader, taking 5 minutes and 33 seconds to install Quake on the 733MHz Mac. For comparison, we used the DVD-RAM drive from a 500MHz G4 to install Quake III again. On this go-around, Quake installed in just 3 minutes and 49 seconds.